Paint stripping composition and method

ABSTRACT

AN ALKALINE PAINT STRIPPING COMPOSITION COMPRISING ONE OR MORE ALKALINE MATERIALS SUCH AS ALKALI METAL HYDROXIDES, CARBONATES, PHOSPHATES, SILICATES, AND AN ACCELERATING COMPOSITION WHICH CONTAINS ETHYLENE GLYCOL MONOPHENYL EITHER AND A PHENOLIC SELECTED FROM PHENOL, O-PHENYLPHENOL, O-METHOXYPHENOL, P-SECONDARY BUTYL PEHNOL, O-ISOPROPYLPHENOL, BISPHENOL A, B-NAPHTHOL, PAMINOPHENOL, P-NITROPHENOL, AND CRESYLIC ACID. DESIRABLY, THE ALKALINE COMPOSITION IS DISSOLVED IN WATER, IN AMOUNTS WITHIN THE RANGE OF ABOUT 0.25 TO 5 POUNDS PER GALLON, AND THE RESULTING AQUEOUS SOLUTION APPLIED TO THE PAINTED SUBSTRATE FOR A PERIOD SUFFICIENT TO EFFECT SUBSTANTIAL LOOSENING OF THE PAINT COATING.

United States Patent 3,681,250 PAINT STRIPPING COMPOSITION AND METHOD Donald P. Murphy, Royal Oak, Mich., assignor to Hooker Chemical Corporation, Niagara Falls, N .Y.

No Drawing. Continuation-in-part of application Ser. No. 686,718, Nov. 29, 1967. This application Sept. 14, 1970, Ser. No. 72,158 The portion of the term of the patent subsequent to Jan. 5, 1988, has been disclaimed Int. Cl. Clld 7/06 US. Cl. 252-158 9 Claims ABSTRACT OF THE DISCLOSURE An alkaline paint stripping composition comprising one or more alkaline materials such as alkali metal hydroxides, carbonates, phosphates, silicates, and an accelerating composition which contains ethylene glycol monophenyl ether and a phenolic selected from phenol, o-phenylphenol, o-methoxyphenol, p secondary butyl phenol, o-isopropylphenol, Bisphenol A, B-naphthol, paminophenol, p-nitrophenol, and cresylic acid. Desirably, the alkaline composition is dissolved in water, in amounts within the range of about 0.25 to pounds per gallon, and the resulting aqueous solution applied to the painted substrate for a period sufficient to effect substantial loosening of the paint coating.

This is a continuation-in-part of copending application Ser. No. 686,718, filed Nov. 29, 1967, now US. 3,553,- 144, issued Jan. 5, 1971.

This invention relates to a composition and method for removing protective coatings from surfaces and more particularly it relates to a novel additive material for increasing the effectiveness of alkaline stripping compositions.

It is commonly the practice to provide various substrates with protective and/or decorative coatings. These coatings include paints, varnishes, lacquers, enamels, and the like and are formulated from numerous and diverse components, including acrylic resins, alkyd resins, epoxy resins, vinyl resins, and the like. As improvements in adhesions and durability of these coatings have been made, their removal after they have been applied, cured, and/ or dried, has become increasingly difiicult. Frequently, particular difiiculties have been encountered when using chemical means to effect removal of such coatings. It has, therefore, become necessary to subject the coated substrates to the action of increasingly stronger chemical compositions for longer periods of time in order to elfect removal of the coating. In many instances, the coating removal or stripping compositions used have had to be of a sufficient strength and/or used for a sufficiently long period of time that there has been an appreciable attack on the substrate to which the coatings are applied. This has been found to be particularly true in the case of coated aluminum articles. \Additionally, however, even in the absence of attack on the substrate, the long contact times required to efiect loosening of the coatings have often been uneconomical.

It is, therefore, an object of the present invention to provide an improved composition for the removal of protective and/or decorative coatings from substrates to which they have been applied.

Another object of the present invention is to provide an improved coating removal composition, which composition is effective in removing protective and/ or decorative coatings in a relatively short time without adverse effect upon the substrate to which the coating is applied.

A further object of the present invention is to provide an improved method for removing coatings from substrates to which they have been applied, which method may be carried out in a relatively short period of time without adverse affect on the substrate itself.

These and other objects will become apparent to those skilled in the art from the description of the invention which follows.

Pursuant to the above objects, the present invention includes a composition useful in removing protective films, which comprises an alkaline composition and an accelerating amount of an accelerator composition, which accelerator composition comprises a phenolic and ethylene glycol monophenyl ether. Broadly, the present invention includes both an aqueous alkaline solution, containing the above composition which is useful as an aqueous paint stripping material, as well as an alkaline concentrate, which concentrate may or may not contain water, and which may be diluted with water to form an aque ous stripping solution having the desired concentration. These aqueous stripping solutions are found to give excellent results in removing or substantially loosening decorative and/or protective films, such as paint, lacquers, varnishes, enamels, and the like, from metal surfaces to which they have been applied. They have been found to be particularly effective in removing such coating materials which contain acrylic, epoxy, vinyl, or alkyd resin coating components.

More specifically, the concentrate material of the present invention contains an alkaline composition, which alkaline composition is present in an amount of at least about 20% by weight of the concentrate. Desirably, the

alkaline composition constitutes from about 70 to 93% by weight of the concentrate composition.

Various alkaline materials may be utilized in the concentrate composition to provide the desired alkalinity, including alkali metal hydroxides, alkali metal carbonates, alkali metal silicates, alkali metal phosphates, and the like. Of these, the sodium compounds are preferred, such as sodium hydroxide, sodium carbonate, sodium silicates, mono-, di-, and trisodium phosphates, tetrasodiurn pyrophosphate, sodium tripolyphosphate, and the like. It will be appreciated, however, that in some instances, similar compounds of the other alkali metals, such as potassium, lithium, cessium, or rubidium, may also be used. Desirably, these alkaline materials are used in combination, the choice of the particular alkaline materials used and their specific amounts, depending upon the properties which are desired in the alkaline stripping solutions formulated from the concentrate. Typically, the alkali metal hydroxides may be present in amounts up to about by weight of the concentrate composition, while the other alkaline materials such as the carbonates, silicates and phosphates, are typically present in amounts up to about 60% by weight of the alkaline concentrate composition. It will, of course, be appreciated that in each instance, the total of the alkaline materials in the concentrate composition will be within the desired ranges as has been indicated hereinabove.

The alkaline concentrate composition of the present invention also contains an accelerating composition, in addition to the alkaline materials as have been described. This accelerating composition comprises a phenolic and ethylene glycol monophenyl ether. The phenolics used are selected from phenol, o-phenylphenol, o-methoxyphenol, p-secondary butylphenol, o-isopropylphenol, Bisphenol A, ,B-naphthol, cresylic acid, p-aminophenol and p-nitrophenol.

With regard .to the above indicated phenolics, it is to be appreciated that the term cresylic acid is intended to refer to various mixtures of the isomeric cresols, i.e., ocresol, m-cresol and p-cresol, as well as to the individual cresols in a more or less pure form. As is known in the art, these mixtures of cresols are derived from either petroleum or coal tar and generally contain, in addition to the cresols, various other hydroxy organics, such as xylenols, as well as tar acids. Desirably, the phenolic is present in the alkaline concentrate composition in an amount within the range of about 1 to 40% by weight of the concentrate with amounts within the range of about to by weight of the concentrate being preferred.

The ethylene glycol monophenyl ether is present in the composition in an amount at least suflicient to solubilize the phenolic in the aqueous alkaline paint stripping composition, formulated from the alkaline concentrate. It is to be appreciated, that the ethylene glycol monophenol ether may be incorporated with the phenolic in the concentrate composition. Where this is done, it is desirably present in an amount within the range of about 1 to 40 percent by weight of the alkaline composition, with amounts within the range of about 10 to 20 percent by weight being preferred. Alternatively, if desired, the ethylene glycol monophenyl ether may be 'added separately to the aqueous paint stripping composition which has been formulated from the alkaline concentrate material. Where this is done, the ethylene glycol monophenyl ether is desirably added to the aqueous paint stripping solution in an amount within the range of about 0.5 to 10 percent by volume of the solution, with amounts within the range of about 1 to 3 by volume being preferred.

In addition to the components indicated hereinabove, the concentrate compositions of the present invention may also include a gluconic acid material. Such material is typically present in the composition in an amount up to about 10% by weight of the composition, with amounts within the range of about 2 to 7% by weight of the composition being preferred. It is to be understood that by the term gluconic acid material it is intended to refer to and include gluconic acid itself, water soluble and/ or water dispersable forms of gluconic acid, such as the alkali metal gluconates and in particular sodium gluconate, glucono-delta-lactone, and the like.

Surface active or wetting agents may also be included in the concentrate composition, typically in amounts up to about 10% by weight of the composition, with amounts within the range of about 0.1 to 7% by weight of the composition being preferred. Various suitable surface active agents of the anionic, nonionic and cationic types may be used, provided they are soluble and effective in the alkaline stripping solutions. In many instances, excellent results have been obtained when using wetting or surface active agents of the phosphate ester type and, accordingly, these materials are preferred. Additionally, sulfated fatty acid derivatives and sulfated fatty acid amide derivatives, as described in US. Pats. 2,528,378 and 2,773,068, as well as sulfated alcohols, such as the sodium sulfate derivative of 2-ethylhexanol may also be used.

Other adjuvants which may be included in the concentrate compositions of the present invention include rinsing or dispersing agents, such as lignin sulfonates, as well as materials to impart a pleasant odor to the stripping composition, such as pine oil, and the like. Typically, these materials are present in the concentrate composition in amounts up to about 10% by weight of the composition.

In formulating the aqueous alkaline paint stripping compositions of the present invention, the alkaline concentrate material, as described above, is dissolved in water in amounts sufiicient to provide the desired alkalinity to effect substantial loosening of the paint or other films to which the composition is applied. Typically, the aqueous alkaline paint stripping compositions of the present invention contain the concentrate compositions in amounts within the range of about 0.25 to 5 pounds per gallon of solution, with amounts within the range of about 1 to 3 pounds per gallon of solution being preferred. As has been previously noted, where the ethylene glycol monophenyl ether has not been included in the alkaline concentrate material, as part of the accelerating composition, this component will, of course, be added to the aqueous stripping solution in amounts as indicated hereinabove. In a most preferred embodiment of the present invention, the aqueous alkaline paint stripping soltuion will contain the alkaline concentrate material, without the ethylene glycol monophenyl ether, in an amount of about 1.5 to 2 pounds per gallon and the ethylene glycol monophenyl ether will be added in an amount of about 1 to 2% by volume of the stripping solution.

In utilizing the stripping compositions of the present invention, the aqueous alkaline stripping solution, formulated as has been indicated hereinabove, is brought into contact with the substrate from which it is desired to remove the paint or similar protective or decorative coating. The contact time required to effect a substantial loosening of the paint from the substrate will, of course, depend upon the nature and thickness of the paint which is to be removed. In some instances, contact times of a few minutes, e.g., 2 to 3 minutes may be sulficient, while with other and more diificultly removable paints, appreciably longer contact times, e.g., 30 minutes or more, may be desirable. Accordingly, it is not possible to give specific contact times which are used, inasmuch as the contact time utilized will, in each instance, be that which will efiect a substantial loosening of the paint on the surface.

In this respect, it is to be noted that it is not essential that the stripping solutions of the present invention remain in contact with the coated substrate for a period suflicient to effect complete removal of the coating from the substrate. It is only necessary that the contact time be sufiicient to effect a loosening of the paint or other film on the surface so that it may then be removed by brushing, high pressure water spray, or the like. Generally, it is desirable that the contact between the stripping solution and the substrate from which the coating is to be removed is effected by immersing the substrate in the stripping solution. In this manner, a thorough and continuous wetting of the substrate by the stripping solution is obtained with little or no loss of stripping solution. In some instances, however, particularly when less difiiculty removable films are involved, other contacting techniques, such as spraying, flooding, brushing or the like may be used.

Desirably, the paint stripping solution is at an elevated temperature when it is brought into contact with the substrate from which the protective film is to be removed. Preferably, the solution is at a temperature which is close to its boiling point with temperatures within the range of about to degrees centigrade being typical. It will be appreciated, however, that in many instances, either higher or lower temperatures, e.g., room temperature, may also be used.

Once the protective film on the substrate treated has been substantially loosened by contact with the stripping solution and the film has been removed from the substrate, either by retaining the stripping solution in contact with the film until complete removal is obtained or by utilizing other removal techniques on the loosely adhering film, the substrate may then be recoated with a new protective film, if desired. Generally, however, it is preferred that the surface first be water rinsed so as to remove any of the alkaline stripping solution which may still be retained on the surface.

It has been found that by using the aqueous alkaline stripping solution described above, in the manner which has been indicated, greatly improved results are obtained in terms of reduction in the time required to effect a substantial loosening of many different types of protective or decorative films, such as paints, lacquers, varnishes, enamels, and the like. The subject stripping solutions are particularly effective in removing protective and/or decorative films containing resins of the acrylic, alkyd, epoxy, and vinyl types. Moreover, it is found that by combining the phenolic with the ethylene glycol monophenyl ether, solubilization of the phenolic in the aqueous alkaline stripping solution is achieved so that the phenolic does not steam distill out of the solution when it is heated. Thus, attack of the alkaline stripping solution on the substrate, and particularly on an aluminum substrate, is greatly minimized.

In order that those skilled in the art may better understand the present invention and the manner in which it may be practiced, the following specific examples are given. It is to be understood, however, that these examples are merely exemplary of the compositions and process of the present invention and are not to be taken as limiting the invention. In these examples, unless otherwise indicated, temperatures are in degrees centigrade and parts and percent are by weight.

In these examples, a conventional appliance grade acrylic paint was applied over a conventional iron phosphate paint base coating on one inch by four inch steel panels, to a thickness of 1.1 mils. An alkaline solution was formulated by dissolving sodium hydroxide in water in an amount of 1.5 pounds/ gallon. Various phenolic additives and ethylene glycol monophenyl ether were incorporated in this alkaline solution and the immersion time in the solution required to obtain substantial loosening of the paint film on the test panels was determined. Using this procedure, the following results were obtained:

Amount Stripping p-Secondary butyl phenol "'{Ethylene glycol monophenyl ether 13 {o-Phenylphenol Ethylene glycol monophenyl ethero-Methoxy phenol "'{Efihylelne glycol monophenyl ether 75 eno Ethylene glycol monophenyl ether 8 16 o-Isopropyl phenol Ethylene glycol monophenyl ether- 17 {Bisphenol A 6 Ethylene glycol monophenyl ether 18 fl-Naphthol 3 75 Ethylene glycol monophenyl ether p-Aminophenyl 19 "{Ethylene glycol monophenyl ether. p-Nitrophenol Ethylene glycol monophenyl ether.

21 Cresylic acid 7 Ethylene glycol monophenyl ether- 1 No efiect in time shown.

In the above examples, the cresylic acid used was a commercial product derived from coal tar, identified as Cresylic EG and having the following analysis:

Percent m-Cresol 46 p Cresol 26 Low boiling xylenols 23 Tar acids 4 While there have been described various embodiments of the invention, the compositions and methods described are not intended to be understood as limiting the scope of the invention as changes therein are possible and it is intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantialy the same results in substantialy the same or equivalent manner, it

intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. A concentrate composition useful in formulating aqueous film removing compositions which consists essentially of an alkaline composition present in an amount within the range of about 20 to 98% by weight of the concentrate composition, said alkaline composition being independently selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, alkali metal silicates and alkali metal phosphates; and an accelerating composition present in an amount within the range from about 1 to 40% by weight of the concentrate composition which accelerator composition consists essentially of ethylene glycol monophenyl ether in an amount within the range of about 1 to 40% by weight of the concentrate composition and a phenolic material present in an amount ranging from 1 to 40%. by weight of the concentrate selected from the group consisting of phenol, o-phenylphenol, o-methoxyphenol, p-secondary butyl phenol, 0- isopropylphenol, Bisphenol A, B-naphthol, p-aminophenol, p-nitrophenol and cresylic acid.

2. The composition of claim 1 wherein the alkaline composition constitutes from about to 93% by weight of the concentrate composition.

3. An aqueous film removing composition which comprises an aqueous solution of the concentrate composition as claimed in claim 1, which concentrate composition is present in an amount within the range of about A to 5 pounds per gallon of the aqueous composition.

4. The composition of claim 1 further comprising a gluconic acid material present in an amount up to 10% by weight of the concentrate composition.

5. The composition of claim 3 wherein the phenolic compound is selected from the group consisting of ophenylphenol, e-naphthol, p-aminophenol and o-isopropylphenol.

6. A method of removing paint and similar protective films from the surface of an article which comprises contacting the article from which the film is to be removed with the aqueous film removing composition as claimed in claim 3 and maintaining the aqueous composition in contact with the surface for a period sufiicient to eifect a substantial loosening of the protective film on the surface.

7. The method of claim 6 wherein the alkaline composition constitutes from about 70 to 93% by weight of the concentrate composition.

8. The method of claim 6 further comprising a gluconic acid material present in an amount up to 10% by weight of the concentrate composition.

9. The method of claim 6 wherein the phenolic compound is selected from the group consisting of o-phenylphenol, fl-naphthol, p-aminophenol and o-isopropylphenol.

References Cited UNITED STATES PATENTS 2,940,877 6/1960 Jaile et al. 134-38 2,971,919 2/1961 Goldsmith 252l58 X 3,284,365 11/1966 Bourean et al. 252l56 3,308,066 3/1967 Murphy et al. 252l58 3,553,144 1/1971 Murphy 252158 3,563,900 2/ 1971 Murphy 252l56 X 3,576,673 4/1971 Charles et al. 134-38 MAYER WEINBLATI, Primary Examiner US. Cl. X.R.

being 7 252156, DIG 18; 134-38 

